Document 1 (JP 2013-235776A) discloses a lighting system including at least one lighting fixture, a dimmer for outputting a dimming signal, and a dimming signal conversion device for converting the dimming signal (duty signal) outputted from the dimmer into a phase control signal and outputting the phase control signal to the lighting fixture.
The dimmer includes a dimmer body with a rectangular box shape to be attached to a wall surface. The dimmer body is provided at its front face with a rotary manual control knob for selecting a dimming level of the lighting fixture. The manual control knob is provided to the dimmer body and is rotatable within a range of manual control positions including a manual control position corresponding to a lower limit value of the dimming level and a manual control position corresponding to an upper limit value of the dimming level. The dimmer generates a rectangular wave signal (duty signal) with a duty cycle corresponding to a manual control position of the manual control knob, and outputs to a dimming signal line the dimming signal being the rectangular wave signal.
Note that, in such lighting systems, there are demands to realize dimming control of changing the dimming level of the lighting fixture automatically depending on brightness of surroundings, in addition to dimming control responding to human manual control, for example. However, it is considered difficult to satisfy the above demands by configurations of the lighting system and the dimming signal conversion device (lighting control device) disclosed in document 1.